The Complete and Updated "Rotifer Polyculture Method" for Rearing First Feeding Zebrafish.

The zebrafish (Danio rerio) is a model organism of increasing importance in many fields of science. One of the most demanding technical aspects of culture of this species in the laboratory is rearing first-feeding larvae to the juvenile stage with high rates of growth and survival. The central management challenge of this developmental period revolves around delivering highly nutritious feed items to the fish on a nearly continuous basis without compromising water quality. Because larval zebrafish are well-adapted to feed on small zooplankton in the water column, live prey items such as brachionid rotifers, Artemia, and Paramecium are widely recognized as the feeds of choice, at least until the fish reach the juvenile stage and are able to efficiently feed on processed diets. This protocol describes a method whereby newly hatched zebrafish larvae are cultured together with live saltwater rotifers (Brachionus plicatilis) in the same system. This polyculture approach provides fish with an "on-demand", nutrient-rich live food source without producing chemical waste at levels that would otherwise limit performance. Importantly, because the system harnesses both the natural high productivity of the rotifers and the behavioral preferences of the fish, the labor involved with maintenance is low. The following protocol details an updated, step-by-step procedure that incorporates rotifer production (scalable to any desired level) for use in a polyculture of zebrafish larvae and rotifers that promotes maximal performance during the first 5 days of exogenous feeding.

Generation time of zebrafish (Danio rerio) and medakas (Oryzias latipes) housed in the same aquaculture facility.

The zebrafish and the medaka are both important model organisms in biomedical research. Both species are frequently characterized as having a generation time of approximately 2-4 months, but the precise onset of sexual maturity and the variability of reproductive success with age have not been previously examined. The authors studied reproduction in replicate groups of wild-type zebrafish (strain AB) and medakas (strain Cab) that were maintained together in the same aquaculture system. Length, weight and survival of the fish were measured and recorded once per week. Reproductive success and viability of offspring were also evaluated. Both zebrafish and medakas began producing viable embryos within 60 d post-fertilization. These findings show that it is possible to successfully maintain populations of both species within the same research infrastructure without compromising reproductive success or embryo viability.